Production of fire extinguishing foam



June 23, 1936. Q MILLER 2,045,400

PRODUCTION OF FIRE EXTINGUISHING FOAM Filed March 5, 1954 Patented June 23, 1936 UNITED STATES PATENT OFFICE Leonard Challinor Miller, London, England, assignor to Merryweather & Sons Limited, London, England Application March 5,

1934, Serial No. 713,985

In Great Britain March 15, 1933 Claims.

This invention has reference to the production of fire extinguishing foam by simple means whereby the foam can be propelled through pipes or hose and projected through a nozzle in the 5 form of a jet to the seat of the fire.

Many proposals have been made for producing fire extinguishing foam by the mingling of air or gas, water and a foam generating or stabilizing powder or liquid, but so far as I am aware these proposed methods have all suffered from one or more of a number of defects e; g. the foam formed has not been suitable, the apparatus has been complicated and expensive or the foam could not be readily propelled through sufiicient length of piping or hose and delivered through a nozzle in the form of a jet.

. It is the object of the present invention to provide an improved apparatus for producing, propelling and projecting fire extinguishing foam. 20 In the improved apparatus gas or air under pressure is entrained, in the form of bubbles, by and mixed with liquid directed in a jet at high velocity into and through a velocity increasing and pressure reducing device, such as an injector cone or Venturi tube and a foam stabilizing solution such as a soap or equivalent solution, supplied under pressure, is introduced into the stream of jet liquid and entrained gaseous medium in the region of reduced pressure and increased velocity.

In order to obtain a satisfactory foam by means of gas or air, without the use of quantities of gas forming chemicals, it is necessary to supply the gas or air to the stream of water at a substantial pressure. Thus with water supplied to the in- 35 jector or Venturi tube at a pressure at the inlet of say 50 pounds per square inch, by supplying thereto gas or air at a pressure of about 10 pounds per square inch 9. very effective foam is formed without the addition of gas forming chemicals and only requiring a comparatively small quantity of a foam stabilizing liquid such as a soap or equivalent solution.

Exhaust gas from an internal combustion engine is preferably used but air or flue gases under suflicient pressure may be used to mix with the liquid and form bubbles or foam.

The accompanying drawing illustrates by way of example one form of apparatus for forming and projecting foam according to the invention, exhaust gas being assumed to be used.

Figs. 1 and 2 are an elevation and plan of the apparatus and Figs. 3 and 4 a section and plan to an enlarged scale of the injector cone or Venturi tube.

The apparatus shown in Figs. 1 and 2 comprises a base having mounted thereon the device shown in Figs. 3 and 4 for mixing water, exhaust gas and foam-stabilizing liquid and propelling the foam thus formed; a tank a for foam-stabilizing liquid; a rotary pump b for delivering the 5 said liquid at a suitable pressure into the stream of water; and an electric motor for driving the pump. A pipe a leads from the tank a to the pump b and'a pipe at from the pump to the mixing and propelling device as shown in Figs. 3 l3 and 4; a is a control valve on the pipe a and d is a pressure gauge on the delivery pipe 11.

-The mixing and propelling device comprises an injector cone or Venturi tube e extending from a chamber ,7 connected at q to a flexible pipe h coupled to the exhaust pipe of an internal combustion engine so as to deliver exhaust gas at a pressure of say ten pounds. In alignment with the cone or tube e is a contracted nozzle 2' connected under control of a valve k to a supply of water under a pressure of say fifty pounds; the nozzle 2' projects through the chamber sufficiently close to the cone or tube e as to leave an annular space through which the gas will pass from the chamber into the cone or tube with the water. The outlet 1 of the cone or tube e is coupled to a length of piping or hose. Foam stabilizing liquid such as a soap solution is pumped from the tank a and introduced at m under suflicient pressure into the stream passing through the cone or tube e. 'I'heproportions of the nozzle 1' and the cone or tube e are so chosen in relation to the size of the water inlet and the foam outlet, that the initial pressure in the flowing stream of water is reduced in the cone or tube to a point sufficiently below the pressure in the exhaust pipe of an igitemal combustion engine'to enable the required amount of exhaust gas to enter the water stream through the annular space surrounding the nozzle. This 40 reduction of water pressure also enables the foam stabilizing solution to be introduced at a less pressure than would otherwise be required.

The several ingredients, namely water, exhaust gas, and the foam stabilizing. solution, pass together to the delivery outlet 1 and thence into piping or hose through which it is propelled and ultimately projected through a nozzle at the point of application.

Water under pressure passing through the 60 Venturi tube may be derived from a hydrant, o a fire engine pump, or any other convenient source of pressure which will propel the mixture through the piping or hose and project the foam with suffcient force for the duty required.

The foaming solution which can be made up of any of the well known foaming subsances in common use, can be introduced into the water stream by means of a hand pump or other feeding device instead of a mechanically operated pump or by means of the exhaust gas pressure. The motor 0 can be conveniently supplied with current from the electric battery of an automobile vehicle when the apparatus is carried on such a vehicle, as for instance a fire engine.

To prevent the possibility of the water pressure causing water toenter the exhaust gas pipe 11 against the inflow of the exhaust gas, a nonretum valve h is provided at the connection a. An adjustable valve .n is provided on a branch from the exhaust pipe as a means of escape for the gas which is not required for foam-forming purposes. It will thus be seen that the proportions of water, exhaust gas and foam stabilizing solution can be varied to suit the desired con- 'sistency of the foam.

:1: indicates diagrammatically in Fig. 2, the internal combustion engine or other source of gas or air under pressure.

With apparatus as described it is found that no f devices for whipping, beating or breaking up the foam are required and the foam produced can be propelled through a long length of hose and projected from a nozzle a considerable distance.

Where, instead of exhaust gas from an internal combustion engine, air under pressure is used it may be derived from any suitable source, for instance an existing compressed air supply, or, where steam or other motive power is available, an air compressor driven thereby may be used. Instead of exhaust gas or air under pressure furnace flue gases may be compressed and led to the water stream.

What I claim is:-

1. In an apparatus for producing and delivering fire extinguishing foam the combination with an injector comprising a Venturi tube having terminal inlet and outlet openings and an additional inlet opening intermediate its ends and a driving nozzle operatively associated with the inlet end of said Venturi tube, of a source of liquid under pressure connected to said driving nozzle, a source of gaseous fluid under pressure connected to the inlet end of the Venturi tube, a source of foam stabilizing solution, means for forcing foam stabilizing solution from said source to and through said additional inlet opening into said Venturi tube and foam conveying means connected to the outlet opening of said Venturi tube.

2. In an apparatus for producing and propelling flre extinguishing foam a chamber, an injector cone connected at its inlet end to said chamber and at its outlet end to foam delivering means, said cone including an auxiliary inlet intermediate its ends, an injector driving nozzle extending through said chamber and directed into the inlet end of said injector cone, a source of liquid under pressure connected to said driving nozzle, a source of gaseous fluid under pressure connected to said chamber and means for introducing a foam stabilizing solution under pressure into said injector cone through said auxiliary inlet.

3. An apparatus as claimed in claim 2, provided with an adjustable escape valve in the connection between the source of gaseous fluid under pressure and the chamber for permitting fluid delivered from the source in excess of what is required for foam producing purposes to escape before coming within the influence of the injector.

4. Apparatus for producing and propelling fire extinguishing foam comprising an injector cone, a contracted nozzle arranged in alignment there with and providing an annular space between said nozzle and injector cone, a chamber surrounding the said nozzle, a source of fluid under pressure connected to said chamber, a tank for containing foam stabilizing liquid, a pump, pipe connections leading from said tank to said pump and from said pump to said injector cone, means for coupling to said nozzle a pressure water conveying hose and means for coupling to said injector cone a foam conveying hose.

5. Apparatus for producing and propelling fire extinguishing foam comprising an injector cone having an outlet, a contracted nozzle arranged in alignment therewith and providing an annular space between said nozzle and injector cone, a 

